1. Field of the Invention
The present invention relates to an apparatus for installing a ventilation fan, especially in a hole bored through a wall of a building and the like.
2. Description of the Prior Art
The present inventor has already proposed in Japanese Laid-Open Patent Publication No. 6-323585, whose patent has been allowed as Japanese Patent No. 2530284, an apparatus for installing a ventilation fan highly effective in attaining crime prevention and antidisaster. This apparatus is applied especially for installing a ventilation fan in a hole bored through a wall of a building and comprises a housing, for fixing a ventilation fan therein, having at a building side an opening covered with a lid able to be open or shut.
The apparatus is now expected to be used under many different environments. Depending on the place where a building provided with the apparatus is located, it is possible that dust outside the building, air pollutant such as nitrogen oxide, poisonous gas and etc. pass through the ventilation fan and come into a room of the building, e.g., located along a road, in a factory zone, a dangerous area or the like.
The object of the present invention is to improve the apparatus in prevention of dust, gas or the like from coming into the building.